Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $197.67   11.169%   $219.7478   $219.75   $219.75   $219.70  
  Purchase #2 $58.47   7.729%   $62.9891   $62.99   $63.00   $63.00  
  Purchase #3 $191.52   7.164%   $205.2405   $205.24   $205.25   $205.20  
  Purchase #4 $174.48   13.702%   $198.3872   $198.39   $198.40   $198.40  
  Purchase #5 $223.48   4.448%   $233.4204   $233.42   $233.40   $233.40  
  Purchase #6 $43.94   5.277%   $46.2587   $46.26   $46.25   $46.30  
  Purchase #7 $54.63   5.589%   $57.6833   $57.68   $57.70   $57.70  
  7 purchase totals = $944.19       $1,023.7270   $1,023.73   $1,023.75   $1,023.70